My Message Handling Functionality in AS

RsblsbShawn · 2008-02-11T15:38:31

My engine is almost fully exposed to AS, but I can't quite figure out the best way to approach using my message handler. Here's how it works: I have a singleton class called "MessageHandler" defined as follows: template <typename T> class MessageHandlerClass : public MessageHandlerPublisher , private NoCopy, public Singleton<MessageHandlerClass> { public: void publish(const T *msg); void subscribe(MessageInterface<T> *l); void unsubscribe(const MessageInterface<T> *l); private: MessageHandlerClass(); ~MessageHandlerClass(); std::vector<MessageInterface<T> *> listeners; std::queue<T *> messages; }; (there's actually more things like delegates and delayed sending, but those aren't important for this discussion). Next there's the MessageInterface Interface/Class: template <typename T> struct MessageInterface { virtual ~MessageInterface() { MessageHandler<T>::Instance().unsubscribe(this); } virtual void receiveMessage(const T *msg) = 0; }; Basically how this works is you can create any message whatsoever.. so for example a player input message like such: struct PlayerIPMsg { PlayerIPMsg() { move_up = move_down = move_left = move_right = false; } bool move_up, move_down, move_left, move_right; }; Then any class can listen for that message... so for example the player: struct Player : public Entity, public MessageInterface<PlayerIPMsg> { Player() { MessageHandler<PlayerIPMsg>::Instance().subscribe(this); } void receiveMessage(const PlayerIPMsg *msg) { //handle movement here; } }; This basically allows any data to pass between objects that have no idea about each other... I can't think of the best way to approach this in AS. I have about 25 base engine Message classes, not including any game-specific ones, so it'd be impractical for each IEntity to implement all message interfaces if it doesn't use them... Any ideas on how I should approach this?

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Started by RsblsbShawn February 01, 2008 01:19 AM

12 comments, last by WitchLord 17 years ago

RsblsbShawn

Author

122

February 03, 2008 11:49 AM

Hmm.. that's unfortunate, because that's one of the primary features I was looking for in a scripting language =(...

At least AS works though, so it beats GM ;)

I wonder what I'd have to "donate" in order for that feature to get implemented =)

Digital_Asphyxia

122

February 03, 2008 05:53 PM

Quote:
Original post by RsblsbShawn
Hmm.. that's unfortunate, because that's one of the primary features I was looking for in a scripting language =(...At least AS works though, so it beats GM ;)

You can probably still accomplish most of what you want by using basic design patterns. It may be require a few extra steps such as the use of interfaces and storing a behavior object in the class but is supported in the language. You might end up with something like:

class A : IEntity { IEntityBehaviour @updateBEH; A() { } void update() {  if(updateBEH != null) {   updateBEH.exec(this);  } }}

Digital_Asphyxia

122

February 03, 2008 06:08 PM

The following example shows how to implement a global factory for instantiation of objects across modules. This is the closest example I have that matches what you described in your original post (replacing an object at runtime). Hopefully this will help you on your journey a little...

#include "angelscript.h"#include "utils.h"static COutStream           out;static asIScriptStruct      *objectFactory = NULL;static const char *const    scriptTest ="IObject @object1;                      \n""IObject @object2;                      \n""IObject @object3;                      \n""                                       \n""interface IObject1                     \n""{                                      \n""   void execute1(int id) const;        \n""   void execute2(int id);              \n""}                                      \n""                                       \n""void DoTest(IObject @object)           \n""{                                      \n""   object.execute1(1);                 \n""   object.execute2(2);                 \n""}                                      \n""                                       \n""void Test1()                           \n""{                                      \n""   IObject @object;                    \n""                                       \n""   @object = objectFactory.create();   \n""   DoTest(object);                     \n""}                                      \n""                                       \n""void Test2()                           \n""{                                      \n""   DoTest(object1);                    \n""   DoTest(object2);                    \n""   DoTest(object3);                    \n""}                                      \n""                                       \n";static const char *const    scriptObject1 ="class Object1 : IObject                \n""{                                      \n""   void execute1(int id) { execute(1, 1, id); }    \n""   void execute2(int id) { execute(1, 2, id); }    \n""}                                      \n""                                       \n""class Object1Factory : IObjectFactory  \n""{                                      \n""   IObject @create()                   \n""   {                                   \n""       execute(1, 0, 0);               \n""       return Object1();               \n""   }                                   \n""}                                      \n";static const char *const    scriptObject2 ="class Object2 : IObject                \n""{                                      \n""   void execute2(int id) { execute(2, 2, id); }    \n""   void execute1(int id) { execute(2, 1, id); }    \n""}                                      \n""                                       \n""class Object2Factory : IObjectFactory  \n""{                                      \n""   IObject @create()                   \n""   {                                   \n""       execute(2, 0, 0);               \n""       return Object2();               \n""   }                                   \n""}                                      \n";static void execute(asDWORD typeID, asDWORD methodID1, asDWORD methodID2){    if(0 == methodID1) {        printf("Creating type %d\n", typeID);    }    else {        printf("Object%d.execute%d() Object%d.execute%d()\n",            typeID,            methodID1,            typeID,            methodID2);    }}static void SetFactory(asIScriptEngine *engine,                       const char *module,                       const char *object){    int typeId = engine->GetTypeIdByDecl(module, object);    if(typeId >= 0) {        asIScriptStruct *obj;        obj = (asIScriptStruct *)engine->CreateScriptObject(typeId);        if(NULL != obj) {            if(NULL != objectFactory) {                objectFactory->Release();            }            objectFactory = obj;        }    }}bool TestXFactory(){    asIScriptEngine     *engine;    int                 r;    engine = asCreateScriptEngine(ANGELSCRIPT_VERSION); assert(NULL != engine);    r = engine->SetMessageCallback(asMETHOD(COutStream,Callback), &out, asCALL_THISCALL); assert(r >= 0);    r = engine->RegisterGlobalFunction("void execute(int,int,int)", asFUNCTION(execute), asCALL_CDECL);    r = engine->RegisterInterface("IObject"); assert(r >= 0);    r = engine->RegisterInterfaceMethod("IObject", "void execute1(int)"); assert(r >= 0);    r = engine->RegisterInterfaceMethod("IObject", "void execute2(int)"); assert(r >= 0);    r = engine->RegisterInterface("IObjectFactory"); assert(r >= 0);    r = engine->RegisterInterfaceMethod("IObjectFactory", "IObject @create()"); assert(r >= 0);    r = engine->RegisterGlobalProperty("IObjectFactory @objectFactory", &(objectFactory = NULL)); assert(r >= 0);    //  Build base test script    r = engine->AddScriptSection("test", NULL, scriptTest, strlen(scriptTest), 0);  assert(r >= 0);    r = engine->Build("test"); assert(r >= 0);    r = engine->BindAllImportedFunctions("test"); assert(r >= 0);    //  Build script 1    r = engine->AddScriptSection("object1", NULL, scriptObject1, strlen(scriptObject1), 0); assert(r >= 0);    r = engine->Build("object1"); assert(r >= 0);    r = engine->BindAllImportedFunctions("object1"); assert(r >= 0);    //  Build script 2    r = engine->AddScriptSection("object2", NULL, scriptObject2, strlen(scriptObject2), 0); assert(r >= 0);    r = engine->Build("object2"); assert(r >= 0);    r = engine->BindAllImportedFunctions("object2"); assert(r >= 0);    //  Object1: Set the factory, run the test, and allocate the first object    printf("Stage 1:\n");    SetFactory(engine, "object1", "Object1Factory@");    r = engine->ExecuteString("test", "Test1()"); assert(r >= 0);    r = engine->ExecuteString("test", "@object1 = @objectFactory.create()"); assert(r >= 0);    //  Object2: Set the factory, run the test, and allocate the first object    printf("\nStage 2:\n");    SetFactory(engine, "object2", "Object2Factory");    r = engine->ExecuteString("test", "Test1()"); assert(r >= 0);    r = engine->ExecuteString("test", "@object2 = @objectFactory.create()"); assert(r >= 0);    //  Object1: Set back to the first object type and create the last object.    printf("\nStage 3:\n");    SetFactory(engine, "object1", "Object1Factory");    r = engine->ExecuteString("test", "Test1()"); assert(r >= 0);    r = engine->ExecuteString("test", "@object3 = @objectFactory.create()"); assert(r >= 0);    //  Test all objects    printf("\nStage 4:\n");    r = engine->ExecuteString("test", "DoTest(@object1)"); assert(r >= 0);    r = engine->ExecuteString("test", "DoTest(@object2)"); assert(r >= 0);    r = engine->ExecuteString("test", "DoTest(@object3)"); assert(r >= 0);    //  If the factory was created release it    if(NULL != objectFactory) {        objectFactory->Release();        objectFactory = NULL;    }    engine->Release();    return (r < 0);}

WitchLord

4,864

February 11, 2008 03:38 PM

Quote:
Original post by RsblsbShawn
I wonder what I'd have to "donate" in order for that feature to get implemented =)

I refuse to be "bribed" into implementing features that I don't think have a place in AngelScript. The only way I can be convinced to implement a feature is to show me that it will make AngelScript better for the majority.

However, I already have plans to make AngelScript more dynamic, it should for example be possible to "inject" new functions into an already compiled module. The intention is to allow modifiable scripts such as what you're describing. I can't say when I'll be able to implement this though.

Regards,
Andreas

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My Message Handling Functionality in AS

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